It is known in the art to utilize positive displacement superchargers having interleaved lobed coacting rotors for supercharging internal combustion engines and for providing compressed air for other purposes. In automotive use, such supercharged engines often emply clutches between an engine connected drive mechanism and the supercharger to disconnect the supercharger drive when supercharged operation is not required. This reduces the parasitic drive loads under many common driving conditions. The clutches are usually hydraulically or electro-magnetically actuated.
Engine oil pressure has been used to hydraulically actuate supercharger clutches. This enables high speed and load actuation, but it has the disadvantage of long external oil lines and multiple connections that increase the complexity and leak potential of supercharger installations. A typical alternative is an electromagnetic clutch, which may be adapted from air conditioner clutches. These systems are relatively low in cost but generally have low torque capacity, so the clutch must be engaged at a fairly low speed. This results in poor highway fuel economy when the supercharger is actuated when not needed.